J-shaped detonating fuse connector



7 March 30, 1965 T. R. ROBERTSON J-SHAPED DETONATING FUSE CONNECTORFiled March 4, 1964 INVENTOR Thomas Russell ROBERTSON AGENT UnitedStates Patent Ofiice E-SHAPED DETGNATING FUSE CONNECTGR Thomas RussellRobertson, Lachnte, Quebec, Canada,

assignor to Canadian Industries Limited, Montreal,

Quebec, Canada, a corporation of Canada Filed Mar. 4-, 1964, Ser. No.349,425 Claims priority, application Canada, June 8, 1963, 877,526 3Claims. (Cl. 102--27) This invention relates to the art of blasting withexplosives and, more particularly, to a novel device for connecting amain or trunk line of detonating fuse to branch lines of detonatingfuse. I Detonating fuse has been used for many years in commercialblasting operations for the purpose of carrying a detonation wave ordetonation impulse to an explosive charge. By detonating fuse is meant afuse consisting of a core of high explosive, such as pentaerythritoltetranitrate (P.E.T.N.), confined within a sheath which normallyconsists of textile material, the said sheath being surrounded by aprotective and reinforcing covering. The high explosive core ofdetonating fuse may consist of from 0.1 to even more than 50 grains ofhigh explosive per foot of length of fuse and the fuse may be made indiameters ranging from about .050 to .250 inch or possibly even larger.The fuse is particularly adaptable to carrying a detonation impulse totwo or more charges of explosive material simultaneously when suchcharges are arranged in a pattern to achieve maximum removal orloosening of earth or rock.

It is a known and common practice to place in close physical contactwith explosive charges in, for example, boreholes, lengths of detonatingfuse. Such length of detonating fuse from each of several chargedboreholes are selected so that they extend outward beyond the loading orcollar end of each borehole. The extended free ends of detonating fuse,which are known in the trade as branch lines, can then be attached toanother length of detonating fuse known as a main or trunk line. Thepattern of detonating fuses so arranged thus describes a single trunkline with two or more branch lines attached at intervals along itslength, each branch line extending to a separate explosive charge. Whendetonation is supplied to one free end of the trunk line detonating fuseby means of, for example, a blasting cap, the detonating impulse iscarried along the trunk line and initiates in turn each attached lengthof branch line detonating fuse. The detonation impulse is thustransmitted nearly simultaneously along each branch fuse to theexplosive charge in each borehole.

Due to the high velocity of the detonation wave propagated along alength of detonating fuse, it is difficult to attach together twolengths of such fuse so that a detonation impulse can be transmittedbetween the two with certainty under all conditions in the field.Experience has shown that in order to accomplish successful transmissionof detonation energy between two connected lengths of detonating fuse,specific procedures must be followed. As detonating fuse is reasonablyflexible and cord-like in construction, it is logical to attach togethertwo adjacent fuse lengths by means of hand-tied knots. However, it hasbeen found that only certain configurations of hand-tied knots can beemployed successfully. Alternatively, connections can be made by variousmethods of coiling together, splicing, etc., lengths of fuse incombination with a securing means, usually by the use of a waterprooftape; otherwise detonation may not propagate between or across thepoints of attachment. In addition, connections between two lengths ofdetonating fuse in trunk and branch lines must be made so that the fuselines lie as nearly as possible at right-angles to one another. It hasbeen found that the lengths of 3,175,491 Patented Mar. 30, 1965detonating fuse beyond the point of attachment must be kept separate toensure propagation of the detonating impulse and guard against thepossibility of the exploding trunk line cutting but not detonating anadjacent branch line.

It can be seen, therefore, that to ensure against the failure of adetonating fuse-initiated system of explosive charges, great reliancemust be placed on the skill and care exercised by the blastingtechnician in preparing the detonating fuse network. Furthermore, theproper preparation of such a network is time-consuming and is oftencarried out in locations and under conditions which, by virtue ofinadequate lighting, imperfect ventilation, high moisture and extremesof temperature, do not contribute to careful preparation.

It is an object of this invention to provide a novel device suitable forconnecting branch lines of detonating fuse to trunk lines of detonatingfuse.

Another object is to provide a detonating fuse congector which can beaffixed quickly and securely in the eld. fAdditional objects of theinvention will appear hereina ter.

The novel detonating fuse connector of this invention consistsessentially of a J-shaped body of thermoplastic material, the longer armof the J having two longitudinal perforations adapted to receive inslidable U-type relationship a continuous length of branch linedetonating fuse, the shorter arm of the J being narrower than saidlonger arm and flexibly abutting said longer arm and being indented inits lower portion so as to receive and securely hold in loopedrelationship the said continuous length of branch line detonating fuse,and the arm-connecting part of the J being also indented so as toreceive a continuous length of main or trunk line detonating fusetransversely of and within said looped continuous length of branch linedetonating fuse.

The connector will be more fully understood by reference to theaccompanying drawing wherein:

FIG. 1 is a perspective view of one form of connector showing twoconnected lengths of detonating fuse in operative relationship;

FIG. 2 is a top view of the connector of FIG. 1 devoid of connectedlengths of detonating fuse; and

FIG. 3 is a plan view of a plurality of branch lines of detonating fuseconnected to a single trunk line of detonating fuse by the connector ofthis invention.

Referring now to FIGS. 1 and 2 of the drawings, there is shown aJ-shaped body of, for example, polyethylene having its longer arm 1provided with two longitudinal perforations 2 and 3 through which isslidably threaded a continuous length of branch line detonating fuse 4.The shorter arm 5 of the J-shaped body which is narrower than longer arm1 flexibly abuts the latter at 6 and is indented at 7 for receiving andsecurely holding detonating fuse 4- in looped relationship. Thearmconnecting part of the J-shaped body is indented at 8 for receiving acontinuous length of trunk line detonating fuse 9 which passes throughlooped detonating fuse 4.

If desired, a flexible thermoplastic strip it! having a small opening 11near its end remote from its point of attachment to longer arm 1 can beinternally molded with longer arm 1 at the side of the back facethereof, in which case longer arm 1 has internally molded therewith asecuring button 12 at its side edge opposite the point of attachment ofstrip It The leading face of button 12 has a size slightly larger incross-section than opening 11 of strip It) so that the latter can beattached to longer arm 1 by forcing or squeezing button 12 throughopening 11. The loop thus formed by the attachment of strip it) tolonger arm 1 serves as retaining means for precut loose ends ofdetonating fuse 4 threading through the connector and thus allows forthe marketing of connector and fuse as a package assembly.

In typical operation in the field where it is desired to connect alength of branch line detonating fuse 4 to a main or trunk line ofdetonating fuse 9 by means of the novel device of this invention, oneend of branch line detonating fuse 4 is passed through perforation 2 inthe direction indicated and then in return direction through perforation3 but only sufficiently far that a free loop is left at the bottom oflonger arm ll. The connector is then placed against detonating fuse g sothat the latter rests within indentation 8 and the free loop of fuse 4is then drawn over shorter arm 5 and squeezed into indentation 7. Thetwo ends of fuse 4 protruding from perforations 2 and 3 above longer arml are then grasped and pulled firmly so as to eliminate any slackness inthe loop going through indentation '7 and thus hold fuse 9 tightly inindentation 8, thus allowing for two firm points of contact betweenfuses 4 and 9.

FIG. 3 of the drawing illustrates a number of connectors, the longer andshorter arms of which are designated as 1a, 1b, 1c and 2a, 2b and 2c,respectively, with branch line fuses 4a, 4b and 4c threadedtherethrough, all providing tight right-angled connections to commontrunk line fuse 9a. In operation, trunk linefuse 9a would be detonatedby means of, for example, a blasting cap (not shown), the detonationimpulse passing along fuse 9a and initiating nearly simultaneously thedetonation of connected branch line fuses 4a, 4b and 4c. The detonationimpulses carried by the latter fuses would then be carried nearlysimultaneously to explosive charges (not shown) in contact with saidfuses.

The connector may be made from any suitable thermoplastic material,including rubber. Polyethylene of a density of about .92 has been foundvery suitable but it will be apparent to one skilled in the art thatother kinds of materials may be successfully employed. It should beappreciated, however, that a material subject to undue hardening in coldtemperatures or subject to undue softening in warm temperatures wouldnot be preferred. Furthermore, a material which readily lends itself tofabrication into the desired shape, such as by moulding or casting bymodern methods, is to be preferred in the interest of economy.

As previously mentioned, the connector may be marketed already attachedor threaded to pre-cut lengths of detonating fuse destined for use forbranch line purposes. ln such a case the measurement of the length offuse to which the connector is attached may be marked on the connector,for example, by printing or embossing on one face of the longer arm ofthe .J-shaped body or on the flexible thermoplastic strip if desired.

In some instances, it is the practice of manufacturers of blastingaccessories to supply pre-cut lengths of branch line detonating fusealready attached to delay devices or relays of various time-delayfactors. With the connector of the present invention, informationspecifying the time-delay factor of such attached relays may also bemarked by printing or embossing on one face of the longer ill arm of theJ-shaped connector or on the flexible tnermoplastic strip if desired.

It will be apparent from the above that the novel detonating fuseconnector of this invention can fulfil a multifold purpose when used inthe field. The blasting technician needs only select the lengths andtype of branch line fuse required, referring for his selection to thelabeling means incorporated with the connector attached to fuse bundleor coil by the manufacturers. Such lengths of branch line fuse may thenbe quickly and easily attached to a main or trunk line of detonatingfuse in any position whatever and by so doing a complete detonating fusenetwork may be simply prepared. An advantage of the detonating fuseconnector of this invention may be found in the fact that no difficulthand-tied knots, taped splices or other such means are required toeffect attachments between fuses nor are any special tools or otherdevices required for the purpose. in addition, the use of the connectorassures tight-fitting right-angled junction points between fuse lines atthe points of attachment such that branch line fuses will not bedislodged from the trunk line either in handling or from the blastelfects from neighbouring explosive charges. Furthermore, almost anyconfiguration of branch line away from the connector may be toleratedbecause the connector holds the branch line at right angles to the trunkline at the crucial point of attachment, thereby ensuring transmissionof detonation impulse between the lines. Because of the moisture andtemperature resistant nature of the material forming the connector, itmay be used under all conditions normally encountered at blasting sites.

What I claim is:

l. A device suitable for connecting a main line of detonating fuse tobranch lines of detonating fuse which consists essentially of a J-shapedbody of thermoplastic material, the longer arm of the J having twolongitudinal perforations adapted to receive in slidable U-typerelationship a continuous length of branch line detonating fuse, theshorter arm of the J being narrower than said longer arm and flexiblyabutting said longer arm and sing recessed in its portion facing saidlonger arm so as to receive and securely hold in looped relationshi thesaid continuous length of branch line detonating fuse, said J-shapedbody also having its bottom part recessed so as to receive a continuouslength of main or trunk line detonating fuse transversely of and withinsaid looped continuous length of branch line detonating fuse.

2. A device as claimed in claim 1 wherein the longer arm of the J hasattached to one side of its back face one end of a thermoplastic striphaving a small opening near its end remote from its point of attachmentto said arm, and the said arm is provided at its side edge opposite thepoint of attachment of said strip with a button adapted to securely holdsaid strip by insertion through said opening.

3. A device as claimed in claim 1 made of polyethylone.

No references cited.

BENlAMlN A. BORCHELT, Primary Examiner.

1. A DEVICE SUITABLE FOR CONNECTING A MAIN LINE OF DETONATING FUSE TOBRANCH LINES OF DETONATING FUSE WHICH CONSISTS ESSENTIALLY OF A J-SHAPEDBODY OF THERMOPLASTIC MATERIAL, THE LONGER ARM OF THE J HAVING TWOLONGITUDINAL PERFORATIONS ADAPTED TO RECEIVE IN SLIDABLE U-TYPERELATIONSHIP A CONTINUOUS LENGTH OF BRACH LINE DETONATING FUSE, THESHORTER ARM OF THE J BEING NARROWER THAN SAID LONGER ARM AND FLEXIBLYABUTTING SAID LONGER ARM AND BEING RECESSED IN ITS PORTION FACING SAIDLONGER ARM SO AS TO RECEIVE AND SECURELY HOLD IN LOOPED RELATIONSHIP THESAID CONTINUOUS LENGTH OF BRANCH LINE DETONATING FUSE, SAID J-SHAPEDBODY ALSO HAVING ITS BOTTOM PART RECESSED SO AS TO RECEIVE A CONTINUOUSLENGTH OF MAIN OR TRUNK LINE DETONATING FUSE TRANSVERSELY OF AND WITHINSAID LOOPED CONTINUOUS LENGTH OF BRANCH LINE DETONATING FUSE.